Unexpected Database Crashes sometimes my astahost databases are down

Sometimes some of my Xisto databases are down. After a couple of hours or a couple of day they are up again. Sometimes all of them are down at the same time, sometimes some of them are up and the other ones are down.The symptom is that when I connect to the forum I have an error message, saying"Parse error: parse error, unexpected '\"', expecting ',' or ';' in /home/../../.../../index.php on line 25"It's not an error in my phpbb because it used to work correctly. So, what happends ? I suppose that the databases crash if the Xisto serer has problem, and that the databases rise up again when the problem is fully solved.But what happends when the problem is partly solved ? In cpanel the database is seen as "OK", but the queries seem not to be served.What can i do ?Yordan